High-sensitivity multifunctional terahertz metamaterial sensor

Abstract

The invention provides a high-sensitivity multifunctional terahertz metamaterial sensor, and belongs to the technical field of terahertz sensing. The sensor is composed of a plurality of metamaterial structure units which are arranged in the same period. The specific structure of each metamaterial structure unit comprises a graphene pattern layer, an indium antimonide dielectric layer and a metal reflecting layer which are sequentially arranged from top to bottom. Wherein the graphene pattern layer is composed of two groups of resonant structures which are nested with each other, and each group comprises four L-shaped strip sheets which are equal in size, biaxial and centrosymmetric. By utilizing the electrical adjustability of graphene and the thermal and magnetic sensitive characteristics of indium antimonide, sensing with excellent performance and diversified functions is realized, and the application range of the graphene / indium antimonide composite material in the terahertz sensing field is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz sensors, and in particular to a highly sensitive multifunctional terahertz metamaterial sensor. Background Art

[0002] Terahertz (THz) waves usually refer to electromagnetic waves with a frequency range of 0.1-10THz, which have the characteristics of low energy, high penetration, transient and non-ionizing. At the same time, due to its wide frequency range and high resolution, terahertz waves can effectively detect substances. These characteristics make terahertz waves have broad application prospects in many fields such as safety detection, material performance research and sensor detection.

[0003] Metamaterial is a man-made electromagnetic material with periodic arrangement of sub-wavelength size, which has unique properties that natural materials do not have, such as negative refractive index, negative magnetic permeability and negative dielectric constant. Natural materials cannot produce effective electromagnetic response in the terahertz band, but metamaterials can interact with them to produce strong electromagnetic coupling effect, and can very sensitively respond to changes in the dielectric constant of the surrounding medium. This characteristic makes metamaterials have great application potential in the field of sensing, and can achieve high-sensitivity detection of small changes in the surrounding environment with high resolution.

[0004] At present, the sensitivity of existing terahertz metamaterial sensors is low and their functions are relatively simple. They can only detect analytes under certain specific environments and cannot expand their application scenarios. Summary of the invention

[0005] The present invention aims to at least improve one of the technical problems existing in the prior art. To this end, the present invention proposes a highly sensitive multifunctional terahertz metamaterial sensor.

[0006] According to the highly sensitive multifunctional terahertz metamaterial sensor of the first aspect of the present invention, the multifunctional terahertz metamaterial sensor is composed of a plurality of identical periodically arranged terahertz metamaterial units; The terahertz metamaterial unit is arranged from top to bottom in the order of a top graphene pattern layer, a middle indium antimonide dielectric layer and a bottom metal reflective layer, wherein: The graphene pattern layer includes two groups of mutually nested resonance units, and the resonance unit includes an inner first resonance structure and an outer second resonance structure; each group of the first resonance structure and the second resonance structure is composed of four equal-sized, biaxial and centrosymmetrical L-shaped strips. According to the highly sensitive multifunctional terahertz metamaterial sensor of the embodiment of the present invention, the quality factor Q can reach up to 64. It can not only sense the refractive index of the object to be measured, but also sense the physical field (heat, magnetism) of the environment and the applied gate voltage. Among them, the refractive index sensitivity can reach up to 830GHz / RIU, and the magnetic field sensitivity can reach 1700GHz / T.

[0007] The highly sensitive multifunctional terahertz metamaterial sensor of the embodiment of the present invention has a flexible control method. For sensing tests in different application environments, its resonant frequency can be dynamically adjusted without changing the material structure to compensate for the deviation of sensor performance caused by manufacturing errors, so that it has higher geometric parameter tolerance.

[0008] The highly sensitive multifunctional terahertz metamaterial sensor of the embodiment of the present invention has a simple structure, is easy to process, and has low requirements on processing precision.

[0009] In a possible implementation of the first aspect, the period of the terahertz metamaterial unit is p=60μm~65μm, which is smaller than the working wavelength. The unit designed based on this period can effectively provide the required resonance characteristics, ensuring the good response of the sensor to terahertz waves. At the same time, it is also relatively easy to implement in the manufacturing process and has a certain geometric tolerance.

[0010] In a possible implementation of the first aspect, the graphene pattern layer of the metamaterial unit is biaxially symmetric and centrosymmetric about the terahertz metamaterial unit structure. The metamaterial unit relies on the symmetric structure to make the sensor insensitive to THz wave polarization, thereby improving the sensitivity and stability of the sensor.

[0011] In a possible implementation of the first aspect, the gap range between the L-shaped strips of the first inner resonant structure is l1=0.5μm~1.4μm, and the width range is w1=3μm~3.5μm; the gap range between the L-shaped strips of the second resonant structure is l2=3.9μm~4.5μm, and the width range is w2=6.5μm~7μm. Reasonable gap and width ranges have a smaller resonant frequency difference and provide a wider geometric tolerance for preparation. Reasonable gap and width ranges can be optimized to improve the sensitivity and selectivity of the sensor, and are also easier to control in the manufacturing process.

[0012] In a possible implementation of the first aspect, the graphene pattern layer uses a single layer of graphene with a thickness of h1=0.34 nm.

[0013] In a possible implementation manner of the first aspect, the thickness of the indium antimonide dielectric layer is in the range of h2=5.1 μm to 5.5 μm.

[0014] In a possible implementation manner of the first aspect, the thickness of the metal reflective layer needs to be greater than its skin depth so as to effectively reflect the terahertz wave, and 0.2 μm is used to save costs.

[0015] In a possible implementation manner of the first aspect, the material of the metal reflective layer is any one of gold, silver, and copper.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a schematic diagram of the overall structure of the highly sensitive multifunctional terahertz metamaterial sensor of the present invention; Figure 2 A three-dimensional schematic diagram of a periodic structure sensor unit structure of the sensor of the present invention; Figure 3 A top view of the unit structure of the sensor of the present invention; Figure 4 is the absorption spectrum of the sensor of the present invention; Figure 5 Absorption spectra of the sensor of the present invention at different Fermi levels; Figure 6 The sensor absorption spectra of the sensor of the present invention at different temperatures; Figure 7 The sensor absorption spectrum diagram of the sensor of the present invention under different environmental refractive indices; Figure 8 It is a linear relationship fitting diagram of the resonant frequency transformation of the sensor of the present invention under different environmental refractive indices; Fig. 9 The sensor absorption spectra of the present invention under different magnetic induction intensities after a magnetic field is applied in the x direction; Fig.10 It is a linear relationship fitting diagram of the resonant frequency transformation under different magnetic induction intensities after the sensor of the present invention is subjected to an external magnetic field in the x direction.

[0019] Reference numerals: graphene pattern layer 1, indium antimonide dielectric layer 2, metal reflective layer 3. DETAILED DESCRIPTION

[0020] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0023] The terms "first", "second", "third", etc. in the specification and claims of the present application and the drawings are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a series of steps or units are included, or optionally, steps or units not listed are included, or optionally, other steps or units inherent to these processes, methods, products or devices are included.

[0024] Only the part relevant to the present application is shown in the accompanying drawings, but not all of the content. Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processing or methods depicted as flow charts. Although the flow chart describes each operation (or step) as a sequential process, many of the operations therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of each operation can be rearranged. When its operation is completed, the process can be terminated, but it can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0025] The terms "component", "module", "system", "unit", etc. used in this specification are used to represent computer-related entities, hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a unit can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or distributed between two or more computers. In addition, these units can be executed from various computer-readable media having various data structures stored thereon. Units can communicate through local and / or remote processes, for example, based on signals having one or more data packets (e.g., data from a second unit interacting with another unit in a local system, a distributed system, and / or a network. For example, the Internet interacts with other systems via signals).

[0026] At present, the sensitivity of existing terahertz metamaterial sensors is not high, and the functions are relatively single. They can only detect analytes in certain specific environments and cannot expand the application scenarios. Therefore, based on the electrical adjustability of graphene and the thermal and magnetic sensitivity characteristics of indium antimonide, the present invention proposes a highly sensitive multifunctional terahertz metamaterial sensor, which can realize the analysis and detection of changes in various objects or physical fields such as refractive index, temperature and magnetic field.

[0027] According to the highly sensitive multifunctional terahertz metamaterial sensor of the first aspect of the present invention, the multifunctional terahertz metamaterial sensor is composed of a plurality of identical periodically arranged terahertz metamaterial units; The terahertz metamaterial unit is arranged from top to bottom in the order of a top graphene pattern layer, a middle indium antimonide dielectric layer and a bottom metal reflective layer, wherein: The graphene pattern layer includes two groups of mutually nested resonance units, and the resonance unit includes an inner first resonance structure and an outer second resonance structure; each group of the first resonance structure and the second resonance structure is composed of four equal-sized, biaxial and centrosymmetrical L-shaped strips. According to the highly sensitive multifunctional terahertz metamaterial sensor of the embodiment of the present invention, the quality factor Q can reach up to 64. It can not only sense the refractive index of the object to be measured, but also sense the physical field (heat, magnetism) of the environment and the applied gate voltage. Among them, the refractive index sensitivity can reach up to 830GHz / RIU, and the magnetic field sensitivity can reach 1700GHz / T.

[0028] The highly sensitive multifunctional terahertz metamaterial sensor of the embodiment of the present invention has a flexible control method. For sensing tests in different application environments, its resonant frequency can be dynamically adjusted without changing the material structure to compensate for the deviation of sensor performance caused by manufacturing errors, so that it has higher geometric parameter tolerance.

[0029] The highly sensitive multifunctional terahertz metamaterial sensor of the embodiment of the present invention has a simple structure, is easy to process, and has low requirements on processing precision.

[0030] It should be noted that the period of the terahertz metamaterial unit is p=60μm~65μm. Preferably, the arrangement period p=60μm, so that it effectively matches the terahertz wavelength and provides the required resonance characteristics. It should be noted that the graphene pattern layer of the metamaterial unit is biaxially symmetrical and centrosymmetrical about the terahertz metamaterial unit structure. The metamaterial unit relies on a symmetrical structure to make the sensor insensitive to THz wave polarization, thereby improving the sensitivity and stability of the sensor.

[0031] It should be noted that the gap between the L-shaped strips of the first resonant structure on the inner side is l 1= The gap ranges from 0.5μm to 1.4μm, and the width ranges from w1=3μm to 3.5μm. Preferably, the gap l1=0.5μm, and the width w1=3μm. The gap between the L-shaped strips of the second resonant structure on the outside ranges from l2=3.9μm to 4.5μm, and the width ranges from w2=6.5μm to 7μm. Preferably, the gap l2=4.1μm, and the width w2=6.5μm, to ensure the best performance of the structure.

[0032] It should be noted that the bottom metal reflective layer has an electrical conductivity of 5.8×10 7 S / m, copper with a thickness of 0.2μm to reduce production costs.

[0033] It should be noted that the material of the metal reflective layer is any one of gold, silver and copper.

[0034] It should be noted that the thickness of the metal reflective layer must be greater than or equal to 0.2 μm to ensure that it can effectively reflect the terahertz wave.

[0035] In this embodiment, the highly sensitive multifunctional terahertz metamaterial sensor of the present invention is as follows: Figure 1 As shown, the sensor is composed of several identical metamaterial structural units arranged in an array, such as Figure 2As shown, each metamaterial structural unit is composed of a graphene pattern layer 1, an indium antimonide dielectric layer 2 and a metal reflective layer 3 from top to bottom. Each graphene pattern layer includes a first resonant structure (inside) and a second resonant structure (outside) of the same shape that are biaxial and centrosymmetrical. The incident terahertz wave resonates efficiently with the surface of the sensor structural unit within a specific frequency range to produce a high Q value absorption peak. On the basis of the original spectral response, it is extended to the field of terahertz sensing, effectively expanding the application scenarios and uses of the device. By deeply combining the intrinsic mechanism of the resonance peak generation and the properties of the device material, the detection types and ranges are further broadened, thereby meeting the high-sensitivity detection requirements for various types of objects to be tested in different environments, and can be used as a refractive index sensor, physical field and gate voltage sensor.

[0036] As a refractive index sensor, when a certain thickness of analytes with different refractive indices are covered on the surface of the graphene pattern layer, or when the entire device is completely immersed in the analyte to be measured, the change in sensor impedance causes a significant shift in the absorption spectrum. In addition, when the external physical field (heat, magnetism) or gate voltage changes, it will directly affect the electromagnetic properties of the constituent materials (such as graphene and indium antimonide) in the terahertz metamaterial sensor, resulting in different degrees of frequency shift in the dual narrowband absorption peaks.

[0037] like Figure 1 The figure shows the overall structure of the sensor. Figure 2 The terahertz metamaterial sensor is composed of a plurality of sensor structural units arranged periodically in the x and y directions, and adjacent sensor structural units are completely identical and have no gaps in between. The sensor structural unit is composed of a top graphene pattern layer, a middle indium antimonide dielectric layer, and a bottom metal reflector.

[0038] like Figure 3 It is a top view of the sensor structure unit. Each of the top graphene patterns is composed of an inner resonant structure and an outer resonant structure nested together. Each group of resonant structures is composed of four equal-sized, biaxial and centrosymmetrical L-shaped strips.

[0039] It should be noted that the thickness of the indium antimonide dielectric layer ranges from h2=5.1 μm to 5.5 μm, preferably, the thickness is h2=5.5 μm, and its dielectric constant can be described by the Drude model: , , in, =15.68 is the high frequency dielectric constant, and represent the damping constant and plasma frequency, respectively; and represent the vacuum dielectric constant and the effective mass of free carriers, respectively. Represents the intrinsic carrier concentration, which can be further expressed using the formula describe, and represent the Boltzmann constant and absolute temperature respectively.

[0040] It should be noted that the top layer graphene material is a single layer graphene with a thickness of h1=0.34 nm, and its conductivity can be described by the Kubo formula: , , , in, , and represent the Boltzmann constant, graphene Fermi level and relaxation time respectively, T and ℏ represent temperature and reduced Planck constant respectively. In the terahertz band, when Under the condition, the conductivity of graphene material can be simplified to the Drude model: , In order to highlight the advantages, features and purposes of the invention, the invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0041] The numerical calculation is realized by using the multi-physics simulation software COMSOL Multiphysics. Periodic boundary conditions are set in the x and y directions to simulate an infinitely arranged periodic array. Perfect matching layers are set in the upper and lower regions of the sensor structure unit to eliminate the influence of reflected terahertz waves. The terahertz wave is incident vertically on the device surface along the negative direction of the z axis, and the electric field is polarized along the x direction.

[0042] Embodiment 1: The terahertz metamaterial sensor has three uses, one of which is used as a refractive index sensor.

[0043] When the temperature of InSb is 200K and the Fermi level of graphene is 1eV, Figure 4 The absorption rate spectrum of the sensor structure unit has an absorption rate of 99.27% ​​and 97.96% at the frequency points of 3.20THz and 3.99THz, basically achieving perfect dual narrowband absorption. Among them, the absorption peak A at the low frequency point (3.20THz) and the absorption peak B at the high frequency point (3.99THz) have very high steepness, and the corresponding full width at half maximum (FWHM) are 0.05THz and 0.13THz respectively.

[0044] Figure 5When the refractive index of the environment is in the range of 1.0 to 1.3, the terahertz metamaterial sensor is completely placed in the environment to be tested, and the absorption curve of the device changes. With the increase of the refractive index in equal steps, the absorption peaks A and B gradually move toward the low frequency direction, and an obvious frequency shift occurs, indicating that the device has a refractive index sensing function.

[0045] The important indicators of sensor performance can be expressed by the quality factor (Q) and sensitivity ( S R ) two parameters, which can be measured by the formula and (Unit: GHz / RIU) is used for calculation, where Δf and Δn are the changes in the resonance frequency and refractive index. The quality factors of the resonance peaks A and B are 64 and 30, respectively, and the refractive index sensitivities are 830 GHz / RIU and 510 GHz / RIU, respectively. Figure 6 Compared with the conventional terahertz metamaterial sensor, the sensor has a steeper sensing curve, higher sensitivity and better sensing performance. The terahertz metamaterial sensor can provide a solution to overcome the problems of low quality factor and low sensitivity.

[0046] Embodiment 2: The terahertz metamaterial sensor has three uses, one of which is used as a gate voltage sensor.

[0047] When the applied voltage changes, the conductivity of the graphene in the sensor structure unit will change accordingly. The change in material properties directly affects the impedance characteristics of the sensor structure unit, causing the resonant frequency point of the sensing curve to shift, thereby achieving the purpose of monitoring and sensing changes in the external environment, and providing a solution for applications in different scenarios.

[0048] When a gate voltage is applied to the sensor structure unit, the electromagnetic properties of the graphene material will change, enabling accurate sensing of gate voltages of different intensities.

[0049] When the sensor structure unit applies a gate voltage, the Fermi level of graphene will change, and the relationship between the two is: , in Represents the characteristic length dimension of graphene , represents the bias voltage, is the Fermi speed. Figure 7, the sensing curves of resonance peaks A and B in the range of 0.4-1.0eV Fermi level. The two resonance peaks have different degrees of red shift and blue shift. The resonance frequency point of peak A has red shifted, and the range of variation is about 0.5THz; the resonance frequency point of peak B has blue shifted, and the range of variation is about 0.7THz. This shows that any resonance peak of the terahertz metamaterial sensor can meet the high sensitivity requirements for sensing different external voltages.

[0050] Embodiment three: The terahertz metamaterial sensor has three uses, one of which is used as a physical field sensor.

[0051] The intrinsic carrier concentration of the indium antimonide material of the sensor structure unit is very sensitive to temperature, thereby changing its relative dielectric constant. When the external temperature changes, the response of the sensor structure unit to electromagnetic waves changes significantly, giving the device temperature sensing performance.

[0052] When the external temperature increases from 200K to 250K in equal steps, refer to Figure 8 , the amplitudes of the resonance peaks A and B remain basically unchanged, and the resonance frequency points move toward the high frequency direction. The adjustable ranges of peaks A and B are 3.2THz~3.39THz and 3.99THz~4.17THz, respectively, which fully reflects the sensitivity of the device to temperature changes and can be used as a terahertz temperature sensor, with potential application value in the field of terahertz sensing.

[0053] When a magnetic field is applied, the dielectric constant tensor of the indium antimonide material in the sensor structure unit will change due to the magneto-optical effect, showing obvious anisotropy, which is particularly significant at terahertz frequencies. For example, when a magnetic field is applied along the x direction, the dielectric constant of indium antimonide changes to a tensor form: , , , When a magnetic field is applied in the x direction and the magnetic field strength increases from 1.1T to 1.4T in equal steps, refer to Fig. 9 , the resonance peaks A and B remain basically unchanged, with only a slight blue shift, but a new resonance peak C appears at 2.09 THz. With the increase of magnetic field intensity, peak C shows an obvious blue shift. The adjustable range of resonance peak C is 2.09 THz~2.44 THz. Since peak C is a specific resonance peak that only appears after the magnetic field is applied, it fully reflects the sensitivity of the device to magnetic field changes and can be used as a terahertz magnetic field sensor, broadening its application range in the field of terahertz sensing.

[0054] The sensor performance is magnetic field sensitivity The formula (Unit: GHz / T) is used for calculation, where: and is the change in resonance frequency and magnetic field intensity. The magnetic field sensitivity of resonance peak C reaches 1700GHz / T, referring to Fig.10 .

[0055] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the invention.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0057] Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Mentioning "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present embodiment application. The appearance of this phrase in various positions in the specification is not necessarily the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It can be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0058] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A highly sensitive and multifunctional terahertz metamaterial sensor, It is characterized in that The multifunctional terahertz metamaterial sensor is composed of a plurality of identical periodically arranged terahertz metamaterial units; The terahertz metamaterial unit is arranged from top to bottom in the order of a top graphene pattern layer, a middle indium antimonide dielectric layer and a bottom metal reflective layer, wherein: The graphene pattern layer includes two groups of mutually nested resonance units, and the resonance units include a first resonance structure and a second resonance structure; the first resonance structure and the second resonance structure are both composed of four equal-sized, biaxial and centrosymmetric L-shaped strips.

2. The highly sensitive multifunctional terahertz metamaterial sensor according to claim 1, It is characterized in that The period of the terahertz metamaterial unit is p=60 μm-65 μm.

3. The highly sensitive multifunctional terahertz metamaterial sensor according to claim 1, It is characterized in that The graphene pattern layer is biaxially and centrally symmetric about the terahertz metamaterial unit structure.

4. The highly sensitive multifunctional terahertz metamaterial sensor according to claim 3, It is characterized in that The gap between the L-shaped strips of the first resonant structure is l 1 =0.5μm~1.4μm, width range is w 1 =3μm~3.5μm, the gap range between the L-shaped strips of the second resonant structure is l 2 =3.9μm~4.5μm, width range is w 2 =6.5μm~7μm.

5. The highly sensitive multifunctional terahertz metamaterial sensor according to claim 3, It is characterized in that The graphene pattern layer is a single-layer graphene with a thickness of h 1 =0.34nm.

6. The highly sensitive multifunctional terahertz metamaterial sensor according to claim 1, It is characterized in that The thickness range of the indium antimonide dielectric layer is h 2 =5.1μm~5.5μm.

7. The highly sensitive multifunctional terahertz metamaterial sensor according to claim 1, It is characterized in that The thickness of the metal reflective layer is 0.2 μm.

8. The highly sensitive multifunctional terahertz metamaterial sensor according to claim 7, It is characterized in that The material of the metal reflective layer is any one of gold, silver and copper.

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